Transcriptome analysis based detection of Plasmodium falciparum development in Anopheles stephensi mosquitoes

The Plasmodium life cycle within the mosquito involves the gamete, zygote, motile ookinete, and the oocyst stage that supports sporogony and sporozoite formation. We mapped the P. falciparum transcriptome as the parasite progresses through the oocyst stage of development on days 2, 4, 6, and 8 post-P. falciparum infectious blood meal. Through these genomic studies, we identified 212 novel transmission stage biomarkers including genes that are developmentally expressed at a single time point and genes that are pan-developmentally expressed at all four time points in P. falciparum oocysts. Validation of a small subset of genes at the transcriptional and translational level resulted in identification of a signature of genes/proteins that can detect parasites within the mosquito as early as day 2 post-infectious blood meal and can be used to distinguish early versus late stage P. falciparum oocyst development in the mosquito. Currently, circumsporozoite protein (CSP), which is detectable only after day 7 post-infection, is the only marker used for detection of P. falciparum infection in mosquitoes. Our results open the prospect to develop a non-CSP based detection assay for assessment of P. falciparum infection in mosquitoes and evaluate the effect of intervention measures on malaria transmission in an endemic setting.